Combination of Surgical Techniques Restores Multidirectional Biomechanical Stability of Acromioclavicular Joint.

Purpose: To measure the multiaxial stability of the acromioclavicular joint before and after transection of the acromioclavicular capsule and coracoclavicular ligaments and after sequential repair of acromioclavicular and coracoclavicular ligaments.

Methods: Biomechanical testing was performed on fresh-frozen human cadaveric shoulders (N = 6). Translational and rotational stability in the vertical and horizontal planes was measured in intact specimens, after transecting the acromioclavicular and coracoclavicular ligaments, and after sequentially performing the following procedures: single-bundle coracoclavicular repair (CCR), modified Weaver-Dunn procedure (WD), and acromioclavicular stabilization (ACS).

Sagittal orientation of coracoclavicular ligament reconstruction affects the stability of surgical repair.

Background: The variation in the anatomic relationship between the coracoid and the clavicle affects the biomechanical stability of coracoclavicular ligament reconstruction (CCLR).

Methods: Three-dimensional computed tomography reconstruction of 85 patients was analyzed. Anatomic landmarks were used to derive the coracoclavicular sagittal reconstruction angle (sRA).

Vertical and Rotational Stiffness of Coracoclavicular Ligament Reconstruction: A Biomechanical Study of 3 Different Techniques.

Purpose: To compare the biomechanical stability of 3 different coracoclavicular reconstruction techniques under rotational and vertical loading using a cadaveric model.

Methods: In total, 12 cadaveric shoulders were used for testing. The native state was first tested then followed by 3 different reconstruction configurations using suture tapes and cortical buttons: coracoid loop (CL), single-bundle (SB), and double-bundle (DB).

Scapulothoracic rhythm affects glenohumeral joint force.

Hypothesis: Musculoskeletal computer models provide valuable insights into shoulder biomechanics. The shoulder is a complex joint composed of glenohumeral, scapulothoracic, acromioclavicular, and sternoclavicular articulations, whose function is largely dependent on the many muscles spanning these joints. However, the range of patient-to-patient variability in shoulder function is largely unknown.

Posterior augmented glenoid implants require less bone removal and generate lower stresses: a finite element analysis.

Hypothesis: Glenoid retroversion can be corrected with standard glenoid implants after anterior-side asymmetric reaming or by using posterior augmented glenoid implants with built-in corrections. The purpose of this study was to compare 2 augmented glenoid designs with a standard glenoid design, measure the amount of bone removed, and compute the stresses generated in the cement and bone.

Methods: Finite element models of 3 arthritic scapulae with varying severities of posterior glenoid wear were each implanted with 4 different implant configurations: standard glenoid implant in neutral alignment with asymmetric reaming, standard glenoid implant in retroversion, glenoid implant augmented with a posterior wedge in neutral alignment, and glenoid implant augmented with a posterior step in neutral alignment.

Glenoid Rim Anatomy: Risk for Glenoid Vault Perforation During Labral Repair.

Background: Injuries to the glenoid labrum frequently require repair with anchors. Placing anchor devices arthroscopically can be challenging, and anchor malpositioning can complicate surgical outcomes.

Purpose: To determine the safe insertion range and optimal insertion angle of glenoid labral anchors at various positions on the glenoid rim and to establish surgical guidelines that minimize risk of anchor perforation.

Patient-specific computer model of dynamic squatting after total knee arthroplasty.

Knee forces are highly relevant to performance after total knee arthroplasty especially during high flexion activities such as squatting. We constructed subject-specific models of two patients implanted with instrumented knee prostheses that measured knee forces in vivo. In vivo peak forces ranged from 2.

Posterior augmented glenoid designs preserve more bone in biconcave glenoids.

Background And Hypothesis: Total shoulder arthroplasty is recommended treatment for severe osteoarthritis of the glenohumeral joint, which often results in excessive posterior wear. Two recent glenoid components with posterior augments have been designed to correct excessive posterior wear and retroversion. Our primary hypothesis was that posterior augmented glenoid designs require less bone removal than a standard glenoid design.

Reverse total shoulder arthroplasty component center of rotation affects muscle function.

Background: Medialization of the glenohumeral center of rotation alters the moment arm of the deltoid, can affect muscle function, and increases the risk for scapular notching due to impingement. The objective of this study was to determine the effect of position of the glenosphere on deltoid efficiency and the range of glenohumeral adduction.

Methods: Scapulohumeral bone models were reconstructed from computed tomography scans and virtually implanted with primary or reverse total shoulder arthroplasty implants.

Augmented wedge-shaped glenoid component for the correction of glenoid retroversion: a finite element analysis.

Background: This study undertook a computational analysis of a wedged glenoid component for correction of retroverted glenoid arthritic deformity to determine whether a wedge-shaped glenoid component design with a built-in correction for version reduces excessive stresses in the implant, cement, and glenoid bone. Recommendations for correcting retroversion deformity are asymmetric reaming of the anterior glenoid, bone grafting of the posterior glenoid, or a glenoid component with posterior augmentation. Eccentric reaming has the disadvantages of removing normal bone, reducing structural support for the glenoid component, and increasing the risk of bone perforation by the fixation pegs.

A quantitative three-dimensional templating method for shoulder arthroplasty: biomechanical validation in cadavers.

Background: Press-fit humeral components for total shoulder arthroplasty have notable potential complications that may be minimized by preoperative templating and improvements in stem design. The purpose of this study was to develop a 3-dimensional templating technique for the humeral stem and to validate this templating in cadaveric specimens.

Materials And Methods: A cylindrical stem and a stem with a rectangular cross-section were selected for templating and force measurements.

Predicting the effect of tray malalignment on risk for bone damage and implant subsidence after total knee arthroplasty.

Tibial tray malalignment has been associated with increased subsidence and failure. We constructed a finite element model of knee arthroplasty to determine the biomechanical factors involved in increasing the risk of subsidence with malalignment. Four fresh-frozen human knees were implanted with a tibial tray and subjected to forces representative of walking for up to 100,000 cycles.

Effect of total knee arthroplasty implant position on flexion angle before implant-bone impingement.

We generated patient-specific computer models of total knee arthroplasty from 10 patients to compute maximum flexion angle before implant-bone impingement. Motion was simulated for 5 different femoral implant positions and 11 different tibial insert positions at 4 different tibial posterior slopes. In the neutral position, the mean maximum flexion angle was 136.

Accuracy of CT-based measurements of glenoid version for total shoulder arthroplasty.

Background/hypothesis: The arthritic glenoid is typically in retroversion and restoration to neutral version is recommended. While a method for measurement of glenoid version using axial computed tomography (CT) has been reported and has been widely accepted, its accuracy and reproducibility has not been established.

Methods: In 33 patients scheduled for shoulder arthroplasty, glenoid version and maximum wear of the glenoid articular surface were measured with respect to the scapular body axis on 2-dimensional- (2D) CT slices as well as on 3-dimensional- (3D) reconstructed models of the same CT slices.